Klystron apparatus



June 3, 1958 D. F. DRlr-:scHMAN ETAL 2,837,686

KLYSTRON APPARATUS 3 Sheets-Sheet 1 Filed 001'.. 1. 1956 .lllll ATTORNEYJune 3, 1958 D. F. DRIESCHMAN ETAL KLYSTRON APPARATUS .'5 Sheets-Sheet 2Filed Oct. l, 1956 el mm@ w oxlm N Ted? Mmmm m V. E T mFAy F T uw@ A abnKLYSTRON APPARATUS 4 3' sheets-sheet 5 Filed Oct. 1, 1956 N y y 5 @mma E0 s N TSF R Nnd./ 0 s 06m w NF. [dmv L A 3 l 9 MMM 2/ a MFM UAS Y 8 0 M2 5 w/ 9 /H 4 2 l www., o 3 M7 2 w 5 ML f y, o 4 w `4 4 4 f 4 0 .u1 1 Qmm 3 z um. 4 .7 4 Mm 4. .4 "H :a mm@ a 2/ 8 8 a 2 2 5 n 0 w 9 @o Unitedltates Fatent O KLvsrRoN APPARATUS Donald F. Driesclnnan, Los Altos,Arthur A. Goldfinger, Palo Alto, andv StanleyF. Mitchell, Millbrae,Calif., assignors to Eitcl-McCullough, Inc., San Bruno, Calif., acorporation of California Application October 1, 1956, Serial No.612,995

14 Claims. (Cl. S15- 5.46)

This invention relates to klystron apparatus and more particularly toapparatus including a klystro-n tube and magnetic circuitry therefor.

As is well known by those skilled in the art, klystrons .normallycomprise an elongated envelope forming a drift tube havingv an electrongun at one end anda collector electrode at the other end. The drift tubeis made` of aplurality of spaced tubular sections forming between themgaps which are surrounded by cavity resonators. lt is also well knownthat the upper frequency level at which a klystron will operate dependsto some extent on the distance between said gaps; the smaller thedistance, the higher the frequency.

An object of this invention is to provide an improved construction forklystrons in which it is desirable to have relatively small spacingbetween adjacent gaps in the drift tube.

When the distance between adjacent drift tube gaps is decreased itnaturally follows that the cavity resonators surrounding the gaps arealso brought closer together. As a result of the crowded positioning ofthe resonators it is impossible to blow enough cooling air between themto accomplish the required heat dissipation.

Accordingly, a further object of the invention is to provide an improvedconstruction for a cavity resonator which permits cooling air to beblown through the inside of the resonator.

Another object of the invention is to provide an improved constructionfor the tuning doors of the cavity resonator whereby cooling air can beblown through the doorsl and thus through the resonator.

An additional object of the invention is to provide an air ductarrangement associated with a klystron and its magnetic circuitry insuch manner as to provide improved cooling and to facilitate insertionand removal of the klystron from the magnetic circuitry.

The compact arrangement of cavity resonators which results from closelyspaced gaps causes, in addition to the heating problem, a problem oftuning the resonators. Normally cavity resonators have therein a tuningmember which is movable radially of the drift tube axis and is operatedby a radially extending tuning shaft. Klystrons of the type underconsideration are surrounded by a magnetic circuit which includes magnetcoils. When widely spaced resonators are used, the magnet coils can bespaced between them so that the tuning shafts can pass between thecoils. are close to each other there is insutiicient' space between thetuning shafts to accommodate coils of sutlicient slze.

Accor-dingly, a further object of the invention is to provide improvedklystron apparatus wherein a magnet coil surrounds a plurality ofcompactly positioned cavity resonators and yet does not interfere withthe shafts or other operating mechanisms for the tuning members in theresonators.

Another object of the invention is to provide improved However, when'the resonators Fatented `lume 3, 1953 magnetic circuitry which permitsinsertion and removal of a klystron with minimum effort and delay.

A further object of the invention is to provide an extremely strong andcompact klystron, and magnetic circuitry therefor having an improvedarrangement for holding the klystron rmly in position.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of the invention. It is to be understood that the inventionis not limited to the disclosed species, as variant embodiments thereofare contemplated and may be adopted within the scope of the claims.

Referring to the drawings:

Figure l discloses an electron tube apparatus with the upper halfessentially in cross section and the lower half essentially in sideelevation with parts broken away.

Figure 2 is a view along line 2-2 of Figure l.

Figure 3 is an enlarged view along line 3-3 of Figure l, with the uppertuning door moved inwardly.

Figure 4 is a bottom view of Figure 3.

Figure 5 is a prospective view of the shroud shown in Figures l, 2 and3. i

Referring in more detail to the drawings, Figure 1 discloses a klystroncomprising an electron gun 6, having a cathode 7, a focusing electrode 3and an anode 9; a collector electrode 10 having cooling ns 11; and adrift tube structure comprising a plurality of spaced tubular sections12, 13, 14 and 15 forming -three gaps therebetween. Drift tube sections12, 13,y 14 and 15 are each pro-vided with radially extending flanges16, 17, 13 `and `19, respectively, which form end walls of cavityresonators that are provided `around the three gaps. A cylinder 21 ofinsulating material such as ceramic surrounds each gap and is sealedbetween adjacent end walls 16-19 to form outer walls of the evacuatedtube envelope.

Additional walls 22, 23, 24 and 2S are brazed respectively to walls 16,17, 18 and 19 `to form outward extensions thereof. The extension walls22-25 have parallel grooves therein in which .resonator side walls 28are brazed.

The resonators are completed by the addition of tuning doors 30 as shownbest in Figures 3 .and `4. Each of 'the tuning doors comprises a hollowrectangular frame having short sides 31, and long sides 32 joined bybridge 33 so as -to form the two apertures 34. Short walls 35 extendinwardly toward ceramic cylinder 21 from the frame sides 31, and longwalls 36 extend inwardly from the frame sides 32. Resilient contactlingers 39"are positioned around the walls 35 and 36 and are held inplace by screws 40. a metal screen wall 41`is brazed acros's the frame'provided by the inn'er edges of walls 35 which are Vstraight and theinner edges of walls 36 which are' curved to t around 'the ceramiccylinder when the tuning door is moved to its inner position as shown inthe upper half of Figure 3. The use of a sieve-like end wall for thetuning door such as is formed by screen 4l forms an irnportant featureof the invention as will be described hereinafter. It vshould beunderstood that during tube opera- In order to complete the ytuningdoors' frequency energy between the internal resonator portion and theexternal resonator portion.

The resilient contact fingers 39 on the tuning doors 30 are in slidingengagement with the resonator end walls 22-25 and the resonator sidewalls 2S sothat the doors can be moved radially of the tube axis towardand away from cylinders 21. Adjustment of the tuning doors isaccomplished by means of threaded shafts 43, each having an annular ange44 rotatably received in a countersunk hole in the bridge portion 33 ofeach tuning door. T he flange 44 is held in place by a cover plate 45secured to the bridge by means of screws 46. Shaft 43 is rotatablyengaged in a threaded aperture 48 formed in a bracket 49 which is heldbetween resonator walls 28 by meansof screws 50. It will be seen fromFigures 3 and 4 that the ends of the cavity resonators are open becausebrackets 49 do not form closures for the resonators but serve merely assupports for the shafts 43. Thus, cooling air can be blown into one endof the resonators, through the tuning doors via apertures 34 and screenwalls 41, and

then out the other end of the resonators.

In Figure l it will be seen that drift tube section has a radiallyextending llange 55 brazed thereto in addition to the flange 19 and itsextension 25. Flange 55 and the extension ange have radially extendinggrooves therein in which reinforcing ribs 56 are brazed. The collectorelectrode 10 has brazed thereto a ange 57 which is insulatinglyconnected to flange by means of a .ceramic cylinder 58 which is sealedbetween the flanges.

It will be understood from consideration of Figure l that an integralmetal structure is formed between drift tube sections 12 and 15 byvirtue of the fact that resonatorend walls 23 and 24 each serves tworesonators and all of the end walls 22-25 are directly connected to eachother by side walls 28. Thus, stresses tending to deform the tube aretaken by the strong metal walls of the resonators rather than by thefour ceramic .cylinders 21 or the sealing means joining them to theadjacent side walls 16-19.

The structure thus far described forms a unitary klystron assemblyalthough some parts such as the tuning doors 30 are external to theenvelope of the tube per se. The klystron assembly is surrounded by amagnetic circuit including a frame of magnetic material comprising endplates 60 and'61 connected by spaced rods 62 which are fixed to theplates by means of screws 63. End plate 60 is apertured at 64 toaccommodate passage of cooling iin structure 11. A cylinder extendsinwardly from plate 60 adjacent to aperture 64 and is held in place byscrews 66. The inner end of cylinder 65 is provided with a flange 67which serves to hold in place a magnet coil 70. The inner end ofcylinder 65 is recessed to provide a shoulder 71 againstwhich is seatedthe flange 55. Flange 55 has around its periphery a V-notch which isengaged by a plurality of screws 72 to hold the klystron secured withinthe magnetic frame. The end plate 61 is provided with a large centralaperture in which a smaller plate 73 is secured by screws 74. Plate 73has a small central aperture surrounding drift tube section 12 and ismade in two halves in order that it may be assembled after the tube hasbeen inserted through plate 61.

In addition to the magnet coil the magnetic circuit includes a secondmagnet coil 75 which is adjustably supported for movement longitudinallyof the axis of the klystron. Supporting means for coil 75 are providedin the form of collars 76 which are slidably received on several of therods 62 where they are held in the desired position by means of setscrews 77. The magnetic circuit is completed by a focusing coil 80 whichis surrounded by centrally apertured plates 81 and S2 of magneticmaterial. Plate 81 is attached to plate 82 by means of screws 83, andplate 82 it attached to the `main magnetic plate 61 by means of screws84. Plates 81 and 82 are made in two halves so they can be assembledaround drift tube section 12.

In order to provide a flow of cooling air through the inside and alongthe outside of the resonators an air duct is provided as indicatedgenerally at 86. Air duct 86 comprises a shroud 37 which forms a coverover one end of the cavity resonators and opens onto the resonators inregistry with the open ends of the resonators. Referring to Figures lthrough 4, it will be seen that plates 89 are placed parallel to theresonator side Walls 28 and brazed between the adjacent end wallflanges22-25 to form an additional wall which cooperates with the side and endwalls to make air channels extending parallel with the resonators. Asshown in Figure 3, plate 89 is omitted adjacent to side resonator wall28 to which the input coupling 90 is connected. Similarly, the plate 89is omitted on the side of the output resonator which receives the outputcoupling 91 as shown in Figure l. Accordingly, there are a total of fourof the plates 89, two on the middle resonator, and one each on the inputand output resonators. As shown in Figures 3 and 4, cooling ns 93 arepositioned between resonator walls 28 and plates 89 and are brazed tothe adjacent plates 22-25.

As shown best by Figure 5, the shroud 87 has an elongated inlet slot 94adjacent one en-d thereof and three apertures 95, 96 and 97 locatedalong the center line of the shroud. Beneath slot 94 the shroud isprovided with a band 98 which rests upon resonator end wall 25 as shownin Figure l. The sides of the shroud are each provided with two holes100 in which screws 101 are received for attaching the shroud to theplates 89.

In addition to shroud 87 the air duct 86 includes a tubular inletportion 103 which is flattened to form a rectangular inner end 104 whichis received within the elongated slot 94 in the shroud. As shown best inFigure 3, the tubular portion 103 is secured to the shroud by means ofscrews 106 extending through tabs 107 and received within threadedapertures provided in the shroud.

` It should be noted that the inlet slot 94 in the shroud is positionedadjacent the output resonator, that is, the resonator nearest thecollector 10, so that this resonator will receive the greatest coolingflow since it is the one in which the greatest heat is developed.

In order to provide additional support for tubular portion 103, a pairof brackets 108 and a pair of brackets 109 are utilized. Each of thebrackets has a curved portion 110 which tits around tubular portion 103.Each of the. brackets is slightly longer than the shortest distancebetween adjacent rods 62. Accordingly, when the brackets are clampedtogether by the screws 111 as shown in Figure 2 they are firmly wedgedbetween the rods 62 to form a tight support for tubular portion 103.

Referring to Figure l it will be seen that shafts 43 on the tuning doors30 do not extend radially beyond the circle formed by the rods 62.Accordingly, it is necessary to provide removable extensions 115. Onlyone such extension has been shown in Figure l but it should beunderstood that an extension is provided for each of the shafts 43. Eachextension 115 is lprovided at its outer end with a knob 116 by which itmay be easily rotated. The inner end of each extension is provided withmeans for transferring torque to its associated shaft 43. A convenientmeans for detachably connecting the extensions and shafts for torquetransfer is to provide a screw-driver blade 117 on the inner end of eachextension 115 and a cooperating slot 118 on the outer end oteach shaft43. Preferably a collar 119 is attached to the outer end of each shaft43` and serves both as a guide for extension 115 and a stop whichdetermines the inner limit to which the associated door 30 can be moved.Since the resonant cavities are so closely spaced, there is notsu'icient room between adjacent tuning shafts 43 in which eiciently toplace separate magnet coils. .ln order to use the single coil 75,radially extending bores 122 are provided therein to provide passagewayfor the tuning means comprising shafts 43 and their extensions 115.

Taser/noe `Corning now to a description `of 'a `procedure for assemblingthe apparatus, the assembly of the magnetic circuit will be consideredfirst, and throughout the description it will be assumed that theapparatus shown in Figure 1 is located in a vertical position withcollector at the bottom and gun -6 at the top. Starting with end plate60, it is preferable first to attach the coil 70 by means ofthe cylinder65. Next, the rods 62 a-re connected to plate 60. Then the brackets 108`and 109 `carrying tubular portion 103 are slid -downwardly between twoof the rods 62. Next, several collars 76 are slid downwardly on rods 62and tightened in place to form supports for the lower edge of coil 75which is next lowered into contact with these collars. Then vadditionalcollars '76 are slid ldown against the upper edge of coil 75 andtightened in place so that the coil is clamped between the upper andlower collars 76. Finally, the end plate 61 minus its inner plate 73 isattached to the upper end of rods 62 by means of -screws 63.

The circuit assembly thus far described forms a permanent socketstructure which need not be disassembled in order to remove an existingklystron and insert a new one.

The klystron is inserted downwardly, collector end first, in theassembled circuit structure previously described. Flange 55 on the tubecomes to rest against shoulder 71 on the cylinder 65 and is fixed inplace by tighteningscrews 72. It should be understoodat the time theklystron is inserted it carries shroud 87 and that the inner diameter ofcoil 7S is sufficient to receive the shroud. ln addition it should beunderstood at the time the klystron is inserted the tubular portion 103of the air duct is withdrawn outwardly so las not to prevent downwardmovement of the shroud. In addition, the tuning shafts 43 are screwedinwardly far enough that their colla-rs 119 will not ystrike coil 75.After the klystron is in place, tubular portion 103 is moved inwardlyuntil its rectangular end 104 is received within slot 94 and is thensecured in place by the screws 166. Then the brackets 103 and 109 areclamped together around the tubular portion by means of screws 111. Nextthe split plate 73 is positioned as shown in Figure l and secured inplace by screws 74. Then, the split plate 82 is positioned in place bymeans of screws S4, and the coil t) and split plate 81 are attached toplate 82 by means of screws 83. ln order to adjust the tuning doors theextensions 115 are inserted through the bores 122 in coil 75 and areengaged with the outer ends of shafts 43.

It should be understood that all metal parts of the klystron are made ofnon-magnetic material so as not to interfere with the field provided bythe magnetic circuit. In the entire apparatus the only parts which aremade of magnetic material are the main parts of the magnetic circuit;namely, plates 60, 61, 73, 31 and 82, the rods 62, and the cylinder 65.

After a klystron has been inserted in the magnetic circuitry as shown inthe drawings, a blower (notV shown) is connected to the outer end of thetubular inlet portion 103 of the air duct 86. Air from the blower passesthrough inlet portion 1ti3 and then into the shroud 87 which directs theair into each cavity resonator where it passes through the sieve-likescreens 41 of the tuning doors. In addition the shroud directs the airthrough the channels containing cooling fins 93. Likewise the shrouddirects air across the input coupling 90, the output coupling 91 and thelresonator walls 28 in which these couplings are mounted Afterperforming its cooling function the air is free, to escape relativelyunrestricted from the magnetic circuit because rods 62 are relativelynarrow `and are widely spaced.

Thus, it will be understood that cooling air flows into one end of eachcavity resonator, through one of the tuning doors, around the ceramiccylinder 21, and out the other tuning door. This cooling feature is ofcourse made possible by the sieve-like screen wall 41 on the tuningdoors 30. The sieve-like wall 41 prevents the passage of any appreciableradio-frequency energy while permitting the passage of air. The basiccriterion in designing the sieve-like wall 41 is to make each apertureand its metal boundary form such a high capacitance that the wall 41appears to the radio-frequency current as a solid member. As a practicalmatter it has been found that the maximum permissible area of theapertures in wall 41 is in general dependent upon the frequency of thecurrent in the resonator. More specifically, the apertures must be ofsmaller area for klystrons designed for a higher frequency range thanfor klystrons designed for a lower frequency range. ln addition, theshape of each aperture and its depth help determine whether or not radiofrequency will leal; through the sieve-like wall d1. For example,increasing the depth of the aperture helps prevent leakage. Thus, ahoneycomb structure would be electrically better `than the thin screenshown in the drawing, but it would be substantially worse from thestandpoint of lair flow.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

l. Electron tube apparatus comprising a klystron -having an air-tightenvelope with an electron gun at one end and a collector electrode atthe other end, a plurality ot cavity resonator portions surrounding saidenvelope intermediate said gun and collector and having open ends, eachtwo adjacent resonator portions having a cornmon wall whereby all of theresonator portions are grouped compactly along said envelope, two tuningdoors mor/ably mounted in each resonator portion, each of said doorshaving a sieve-like wall forming a part of the inner surface of itsrespective resonator portion, a shroud opening onto said resonatorportions in registry with the open ends of said resonator portions, saidshroud having an inlett aperture therein adjacent the 'resonator portionnearest said Collector, a magnetic circuit surrounding said envelope andcomprising a frame including end plates spaced along the lrlystron axisand extending transversely of said axis, spaced rods interconnectingsaid end plates and arranged around the klystron axis substantiallyparallel to said axis, an annular magnet coil encircling said resonatorportions, adjustment means for moving said tuning doors, said coilhaving bores extending therethrough for receiving the adjustment meansfor the tuning doo-rs in said resonator portions, and means adjustablysupporting said coil on said rods for movement llo'ngitudinally of thetube.

2. A klystron comprising an envelope having an electron gun at one endand a collector electrode at the yother end, a drift tube interposedbetween said gun and said collector, said drift tube comprising spacedtubular sections forming a gap, a cavity resonator portion formedinternally of said envelope and comprising end walls extending radiallyfrom said tubular sections and a cylinder of insulating materialsurrounding sm'd gap and sealed between said end walls to form theoutside wall of said internal resonator portion, a cavity resonatorportion external to said envelope and comprising a rst pair of wallsforming external extensions of said end walls, a second pair of wallsconnected between said first pair of walls, said second walls bein-gspaced externally of said cylinder and positioned on opposite sides ofthe cylinder, tuning doors positioned within said rst and second wallson opposite sides of said cylinder and forming the outer walls of saidexternal resonator 'portion, and means for moving said tuning doorstoward and away from said cylinder, said outer walls formed by saidtuning doors being made of metal screen, whereby cooling air can beforced into said external cavity portion through one of said doors,around said cylinder and out through the other of said doors.

3. An electron tube comprising a vacuum-tight enverope with an electrongun at one end and a collector electrode at the other end, a cavityresonator portion' s'urrounding said tube externally of said envelopeand intermediate said gun and said collector, and a tuning door movablymounted in said `resonator portion, said tuning door comprising asieve-like portion forming part of the inner surface of said resonatorportion.

4. Electron tube apparatus comprising a klystron having a vacuum-tightenvelope with an electron gun at one end and a collector electrode atthe other end, a cavity resonator portion surrounding said klystron'externally of said envelope and intermediate said gun and collector,said resonator portion being open at opposite ends, two tuning doorsmovably mounted in said resonator portion and each having a sieve-likeportion forming part of the inner surface of said resonator portion, andan air duct having one end opening onto said resonator portion inregistry with one of said open ends.

5. Electron tube apparatus comprising a beam-type electron tubecomprising an envelope having an electron gun at one end and a collectorelectrode at the other end, a drift tube interposed between said gun andsaid collector, said dritt tube comprising spaced tubular sectionsforming a gap, a cavity resonator portion formed internally of saidenvelope and comprising end walls extending radially from said tubularsections and a cylinder of insulating material surrounding said gap 'andsealed between said end walls to form the outside wall of said internalresonator portion, a cavity resonator portion external to said envelopeand comprising a first pair of walls forming external extensions of saidend walls and a second pair of walls connected between said rst pair ofwalls, said second walls being spaced externally of said cylinder andpositioned on opposite sides of the cylinder, an additional wallconnected between said rst pair of walls and spaced outwardly from oneof said second walls to form an air channel in cooperation with said onesecond wall and said tirst pair of walls, tuning doors movablypositioned within said 'irst and second walls on opposite sides of saidcylinder, said tuning doors each having a sieve-like portion formingpart of the inner surface of said external resonator portion, theexternal resonator portion yformed by said iirst and second walls beingopened at its ends, and a shroud attached to said tube and opening ontoone of said open ends of the external resonator portion and the adjacentend of said channel.

6. Electron tube apparatus comprising a beam type electron tube having avacuum-tight envelope with an electron gun at one end and a collectorelectrode at the other end, a cavity resonator portion surrounding saidenvelope intermediate said gun and collector, a tuning door movablymounted in said resonator portion and having a sieve-like portionforming part of the inner surface of said resonator portion, adjustmentmeans for moving said tuning door toward and away from said envelope, amagnetic circuit surrounding said tube comprising a magnet coilencircling said resonator portion, said coil being provided with aradially extending bore for the reception of said tuning means, and ashroud opening on to said resonator portion in substantial registry withsaid tuning door, said shroud having an aperture therein in substantialalignment with the bore in said coil.

7. Electron tube apparatus comprising a beam type electron tube having avacuun -tight envelope with an electron gun at one end and a collectorelect-rode at the other end, a cavity resonator portion surrounding saidenvelope intermediate said gun and collector, a tuning door movablypositioned in said resonator portion for movement toward and away fromsaid envelope, means forming a threaded opening at one end of saidresonator portion, a threaded adjustment shaft received Within saidthreaded bore and rotatably secured to said tuning door, a magneticcircuit ysurrounding said tube comprising a magnetcoil encircling saidresonator portion, said coil having a bore extending radiallytherethrough in substantial alignment with said shaft, and an adjustmentshaft 8 extension receivable in said bore 4in the magnet coil, saidshaft and said extension being easily separated one from the other andhaving inter-engaging means for transmitting torque therebetween.

8. Magnetic circuitry `for a klystron, said circuitry comprising a framehaving two end plates of magnetic material, means connected to saidplates and holding them spaced one -from the other, said connectingmeans being of magnetic material and being positioned to surround asubstantial open space, a magnet coil supported on said frame andpositioned between said plates within the space surrounded by saidconnecting means, said coil being in substantial parallelism with saidplates, a bore extending through said coil from its inner periphery toits outer periphery, and an air duct extending into said spacesurrounded by said connecting means, and adjustable clamping-meanssupporting said duct on said magnetic frame for movement toward and awayfrom the center of said open space in a plane substantially parallel tosaid plates.

9. Magnetic circuitry for a klystron, said circuitry comprising a framehaving two end plates of magnetic material, a plurality of rodsinterconnecting said plates and arranged in a circular array, collarsadjustably positioned on some of said rods, a magnet coil positionedwithin the circle -formed by said rods and held in place by engagementbetween the collars on said rods, an air duct extending into the circleformed by said rods, and means adjustably supporting said duct betweentwo of said rods for adjustment inwardly and outwardly of said circle.

l0. Magneti-c circuitry for a klystron, said circuitry comprising amagnetic frame including two centrally apertured end plates, meansinterconnecting said plates and holding the plates in spaced parallelrelation, a cylinder of magnetic material attached to one of said platesand extending toward the other plate, said cylinder having a recessforming an annular shoulder therein, a threaded aperture in saidcylinder opening inwardly to said recess and a screw in said aperture, alirst magnet coil surrounding said cylinder, and a second magnet coilpositioned within the boundary formed by said connecting means andspaced from said first coil toward said other end plate, said secondcoil having a bore extending therethrough from its inner periphery toits outer periphery.

ll. A ldystron comprising an envelope having an electron gun -at one endand a collector electrode at the other end, a drift tube interposedbetween said gun and said collector, said drift tube comprising spacedtubular sections forming gaps therebetween, a cavity resonator portionfor each of said gaps formed internally of said envelope and comprisingend walls extending radially from said tubular section and a cylinder ofinsulating material surrounding each of said gaps and sealed between twoof said end walls to form a vacuum-tight wall for the respectiveresonator portion, cavity resonator portions external to said envelopeand each comprising a first pair of walls forming integral extensions ofsaid end walls, each of said external portions further comprising asecond pair of walls rigidly connected between said first pair of walls,said second walls being spaced externally of their respective insulatingcylinder and positioned on opposite sides of the cylinder, and amounting plate rigidly joined to said extension wall which is closest tosaid collector.

l2. A klystron as claimed in claim l1, in combination with magneticcircuitry comprising a frame of magnetic material including twocentrally apertured end plates, means interconnecting said plates andholding the plates in spaced paraliel relation, a cylinder attached toone of said plates and extending toward the other plate, said cylinderhaving a recess forming an annular should-er therein, a threadedaperture in said cylinder opening inwardly to said recess, and a screwin said aperture, said ltlystron being received within said magneticcircuitry and said mounting plate on the klystron having a V- groovetlterearound into which said screw projects.

13. A klystron comprising an'envelope having an electron gun at 'one endand a collector electrode at the other end, a drift tube interposedbetween said gun and said collector, said-drift tube comprising spacedsections forming gaps therebetween, a cavity resonator portion for eachof such gaps formed internally of said envelope and comprising end wallsextending radially from said tubular section and a cylinder ofinsulating material surrounding each of said gaps and sealed between twoof said end walls forming a vacuum tight wall for the respectiveresonator portions, cavity resonator portions external to said envelopeand each comprising a irst pair of walls forming integral extensions ofsaid end walls, each of said external portions further comprising asecond pair of walls rigidly connected between said rst pair of walls,said second pair of walls being spaced externally of their respectiveinsulating cylinder and positioned on opposite l0 sides of saidcylinder, another wall positioned externally of one of said second pairof walls and between said rst pair of walls to form a channel, and meansfor blowing air through said channel.

14. A klystron as claimed in claim 13 wherein a cooln is positionedwithin and attached to the inner surface of said channel formed by saidfirst pair of walls, said one of said second pair of walls, and saidthird wall.

References Cited in the le of this patent UNITED STATES PATENTS2,293,387 Haeff Aug. 18, 1942 2,410,109 Schelleng Oct. 29, 19462,425,748 Llewellyn Aug. 19, 1947 2,619,611 Norton et al. Nov. 25, 1952

